Java: saved settings with Preferences not restored when a GUI application starts

In my Java app, I have a number of saved values and settings that I would like to get as soon as the application starts. All these values are supposed to be stored in a singleton.
For example, I have a JDialog, where I save a path to my file using this:

But the values are not initialized from the Preference class. "CHECK DEFAULT" shows empty string. I do not understand why and whether there is a better practice of restoring all saved values when a GUI application starts.